We are not aware of any art which discloses the process of this invention. British Pat. No. 2,116,990 (also U.S. Defensive Publication T103,703) to ICI and H. M. Colquhoun, Polymer Preprints, 25 (2), 17-18 (1984), disclose a process for the preparation of poly(ether-ketones) (a) from dicarboxylic acids and aromatic compounds or (b) from monocarboxylic acids or (c) from a mixture of (a) and (b). It should be noted that the process disclosed in these references (1) does not utilize an oxide of phosphorus in any way, (2) is limited to special `activated` dicarboxylic acids, monocarboxylic acids, and aromatic compounds, and (3) does not include such common dicarboxylic acids as terephthalic and isophthalic acids and such aromatic compounds as diphenyl ether or biphenyl (see page 2 lines 55-67 of the British patent). In Example 6 of the British patent, an attempt is made to prepare the poly(ether-ketone) from terephthalic acid and p-diphenoxybenzene in only trifluoromethanesulfonic acid (no oxide of phosphorus) at ambient temperature for 48 hr. No increase in solution viscosity was observed. Subsequently, the mixture was heated to 90.degree. C. for 5 hr with only a slight increase in solution viscosity apparent. We have found that the addition of P.sub.2 O.sub.5 to such a polymerization surprisingly gives a very high solution viscosity in only 10 minutes at ambient temperature (see Example 1 herein). Furthermore, the Colquhoun paper states in column 2 of page 17 that "Terephthalic acid, for example, fails to react at all with aryl ethers in CF.sub.3 SO.sub.3 H, . . . ".
U.S. Pat. No. 4,396,755 discloses a process which involves the polymerization of (a) a dicarboxylic acid(s) with an aromatic compound(s), (b) a self-polymerizable aromatic monocarboxylic acid, or (c) a mixture of (a) and (b) in the presence of a fluoroalkanesulfonic acid and a quinquevalent phosphorus halide, such as PCl.sub.5. According to column 2, lines 20-21, "Presumably, the reaction proceeds via the in-situ formation of mono- or diacyl halide." (Di)carboxylic acid halide(s) are well known intermediates for the preparation of polyketones (see U.S. Pat. No. 4,398,020).
British Pat. No. 2,099,006 discloses a process for the preparation in trifluoromethanesulfonic acid of poly(ether-ketones) from monocarboxylic acid chlorides (such as 4-phenoxybenzoyl chloride) in which P.sub.2 O.sub.5 and water may, if desired, be added to the polymerization reactor in order to produce phosphoric acid (to act as a solvent) (see lines 27-41 on page 1 and lines 1-8 and 17-20 on page 2). In this case, however, only the acid chlorides, which are appreciably more reactive than the carboxylic acids, are disclosed. The use of monocarboxylic or dicarboxylic acids is not disclosed.